What is the concentration of sodium ions in 0.300 M Na₃PO₄?

Answer 1

Na₃PO₄ dissociates to 3Na⁺ + PO₄^3-

So for each 1 mol of Na₃PO₄ you get 3 moles of Na⁺

Final concentration of Na⁺ = 3 x 0.300 M = 0.900 M